The present invention relates to a process of pyrolytically converting carbonaceous feed material into primarily gaseous products, and, more in particular, to pyrolytic conversion of such feed materials into primarily pipeline gas without producing excessive amounts of hydrogen.
Pipeline gas is a fuel gas which consists primarily of methane with some ethane and smaller amounts of higher molecular weight gases. These hydrocarbons have a heat content per unit volume which is much higher than the heat content per unit volume of hydrogen.
The following table illustrates differences in heat content on a unit volume basis:
______________________________________ Heating Value BTU/Ft.sup.3 of Gas (BTU/Ft.sup.3) Contained Hydrogen ______________________________________ CH.sub.4 1013 507 C.sub.2 H.sub.6 1792 597 C.sub.2 H.sub.4 1614 807 H.sub.2 325 325 ______________________________________
With the heating value of hydrocarbons on a unit volume basis being higher than hydrogen, fuels rich in hydrocarbons can be transported through pipelines much more economically than hydrogen. Hydrogen is hazardous and hydrocarbons can be transported in pipelines more safely than hydrogen. In sum, hydrocarbon gases are much more preferable as a fuel than hydrogen.
The manufacture of pipeline gas from carbonaceous material such as coal is becoming increasingly attractive, especially in view of the fact that the ratio of natural gas reserves to production has been diminishing. Conversion of carbonaceous materials to pipeline gas is also attractive because of the tremendous waste disposal problems facing many areas.
Economies of converting carbonaceous materials such as coal into pipeline gas, however, have made conversion by standard techniques very unattractive and as a consequence very little, if any, pipeline gas from the gasification of carbonaceous materials is produced today on a commercial basis.
One of the problems in economic conversion of carbonaceous feed to pipeline gas is in the very unstable nature of the hydrocarbon product gases at high temperatures. For example, it is reported that the half life of ethane at 1500.degree. F. is about 0.7 seconds. Some higher molecular weight hydrocarbons decompose even more rapidly.